It is a known manufacturing method for offset printing plates (Japanese Patent JP S51-8045) in which the base paper is coated with a water resistant middle layer and then on the top of the water resistant middle layer coated with a hydrophilic surface processing solution with a mixture of alginate and colloidal silica to form a water resistant layer by reacting with a polyvalent metallic salt at the surface and/or inside of the water resistant middle layer.